Extracortical origin of some murine subplate cell populations

Abstract

The subplate layer, the deepest cortical layer in mammals, has important roles in cerebral cortical development. The subplate contains heterogeneous cell populations that are morphologically diverse, with several projection targets. It is currently assumed that these cells are generated in the germinative zone of the earliest cortical neuroepithelium. Here we identify a pallial but extracortical area located in the rostromedial telencephalic wall (RMTW) that gives rise to several cell populations. Postmitotic neurons migrate tangentially from the RMTW toward the cerebral cortex. Most RMTW-derived cells are incorporated into the subplate layer throughout its rostrocaudal extension, with others contributing to the GABAergic interneuron pool of cortical layers V and VI.preplate | cell migration | pallium | projecting cells

Secondary expansion of the transient subplate zone in the developing cerebrum of human and nonhuman primates

“…Because of regional differences in the magnitude of corticocortical connections in primates, the width of the SP is highly variable and is particularly large subjacent to the association areas. It should be recognized that the present findings apply to Old World Primates macaque and human, as there are considerable species-specific differences in terms of cell origin and dynamics of migration (17,18). The present investigation was focused on the expansion of the SP zone, as this is one of the most dramatic transient events in the evolution of the human cerebral cortex.…”

“…This phase corresponds to monkey developmental period E54-E59. After this period, the SP continues to increase in size (15)(16)(17)(18)(19)(20) and is characterized by cell differentiation and increase in fiber ingrowth and enlargement of the neuropil. In NHPs, this corresponds to ∼E60-E82.…”

Parsing out the embryonic origin of subplate cell-type diversity

“…The report by Pedraza et al (11) provides a significant advancement to our current knowledge of early neuronal subtype diversity and paves the way to ask further fundamental questions in an effort to unravel the logic underlying wiring of the brain.…”

“…First, Pedraza et al (11) provide the first in vivo evidence that projection neurons can undergo tangential migration, a migratory mode generally ascribed to GABAergic interneurons. Thus, a systematic comparison of the gene-expression profile between RMTW-derived subplate cells and GABAergic interneurons should provide valuable insights into the genetic programs that support this type of migration.…”

“…However, in vivo evidence of this process was previously lacking. The findings by Pedraza et al (11) indicate that some murine interneuron subtypes that populate the deep layers of the brain are derived from pallial sources. It would be interesting to assess the biochemical and intrinsic electrophysiological properties of RMTW-derived interneurons to determine whether these interneurons are similar to previously described subtypes or whether they constitute an entirely new class.…”